The present invention concerns a process for the pseudo-synchronization of a time multiplexing communication network, and uses of that process for example in radiotelephony, for the synchronization of a mobile station with a fixed station upon transfer from a communication between the mobile station and a first fixed station to a communication between the mobile station and a second fixed station, or for geographically locating a mobile station either by fixed stations or by the mobile station itself.
There are time multiplexing radiocommunication networks which comprise a series of fixed stations which are individually synchronized with one or more mobile stations by means of timing signals. Time multiplexing assumes that each of the mobile stations which is in communication with a fixed station has time windows during which it can transmit its messages to the fixed station. In order to synchronize message transmissions by the mobile station with the moments at which the corresponding time window is available at the fixed station, the fixed station emits synchronization signals which permit it to measure the propagation time of a signal between that station and the mobile station and in consequence to control the transmission means of the mobile station.
In the most general case, the fixed stations are not synchronized with each other so that, when the mobile station moves and in consequence has to switch over from communication with one fixed station to communication with another fixed station, it is then necessary to effect synchronization of the mobile station with the new fixed station in order to be able to ensure communication therebetween in the proper time window. In another respect, in the case of a radiotelephony network, synchronization of the mobile station with the fixed station is achieved by passing the synchronization signals over the channel serving for the telephone communication itself, so the conversation between two users is interrupted during the synchronization time.
While synchronization of the fixed stations with each other has been envisaged, in order to be able to effect the transfer of a communication from one fixed station to another without interrupting an ongoing telephone conversation, synchronizing fixed stations with each other in that way is extremely burdensome and cannot be guaranteed to be achieved in a precise fashion in the case of a network covering a large area, by virtue of the possible accumulation of errors resulting from synchronization of the stations in a chain or sequential mode.